Youth in Grades 6 and 7 (N = 186; 78% low-income; 74% non-White) reported the quality of their experiences in their primary afterschool activity over a two-year period. Youth reports of more positive experiences (a composite that included emotional support from adult staff, positive relationships with peers, and opportunities for autonomy) were associated with relative gains in work habits, task persistence, and prosocial behavior with peers as reported by classroom teachers. Examination of specific aspects of experience indicated that perceived emotional support from adult staff was more strongly associated with changes in adolescent functioning than the other aspects of program experience. These findings suggest that youth reports can provide a useful window into the quality of afterschool settings. (author abstract)